The present disclosure generally relates to a control circuit for a power converter and, more particularly, to the control circuit with a reduced number of package pins.
With the progress of the technology, electronic elements may be downsized to fit in the limited space of the electronic devices. For example, the integrated circuit (IC) element comprising a die encapsulated by a package is frequently utilized in the electronic devices. The IC element is usually coupled with other circuit elements through the package pins, and therefore a large-size package is usually needed for accommodating the required number of the package pins. In this situation, the die size is usually much smaller than the size of the package. Not only the wasted package materials result in environmental issues, but also the dimension of the IC element may not be reduced effectively.
In the field of power converters, e.g., AC to DC (AC-DC) power converters and DC to DC (DC-DC) power converters, when the control circuit of the power converter is realized with an IC element, the die size of the control circuit is usually small compared with the size of the package. The control circuit, however, needs many pins to be coupled with other circuit elements, to configure the power stage circuit of the power converter, to receive feedback signals, to receive operation parameters, etc. The package encapsulating the die of the control circuit must have enough pins, which are usually accompanied with the increase in the package size. The design flexibility is therefore constrained.
Some try to reduce the required pin number and the package size of the IC elements by utilizing one or more shared pins. Because the characteristics of IC elements are different, there are no clear rules which may be applicable universally. The circuit blocks of the IC element with a shared pin must be carefully designed to ensure the correct functionality of the IC element.